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OMG \DAQ 3005 problem reading LVDT voltages

Hello everyone....  I'm having a very frustrating time reading simple LVDT data with a DAQ 3005 and DasyLab...  I'm a structural engineer with limited DAQ experience, so I'd appreciate any help you might provide.  

 

The situation is as follows...    I have two LVDT's (OMEGA LD620-15's) putting out +- 5V data as input to a OMEGA DAQ 3005 / DasyLab 11.0 combination.    Reading the raw voltages from the LVDT's seems normal with voltages matching what I'd expect for differential movements of the LVDT's.    

 

The drivers for the DAQ 3005 seems to have installed correctly and I can select the DAQ 3005 as an input module within Dlab.   I have an input module selected for the DAQ 3005 on a worksheet within DLab, along with voltage meters and a scaling module to convert the voltages to .001 inches.    DLab starts and the readings seem somewhat normal, EXCEPT for a voltage drift; looking somewhat like noise.     

 

I'm thinking this may revolve around the "A" common line on the DAQ 3005...   should this be grounded?    I've tried setting the module up as both differential inputs and as single voltage inputs, but the signal still seems to drift.    Meanwhile, readings on the LVDT ouput with a simple digital VOM indicates the LDVT ouput is consistent and constant.     It appears this is a problem with my understanding of how to hook up the DAQ 3005, etc.    Calls to Omega unfortunately, haven't resulted in much help.

 

Thanks in advance,

 

Dave

 

 

 

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Could you please add a chart recorder and show a picture of the noise?

 

Also could you please tell me what the sample rate/blocksize is?

 

Tom Rizzo
InSyS Corp.
www.insyscorp.com
Your DASYLab integrator
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From my IOtech expert:

 

This should be a no brainer. Set the inputs to differential and connect the green wire to Low and the yellow to High. From what I’ve read on line, the transducer is isolated so it should behave like a battery. So, I suggest for the customer to connect a 1.5 volt battery to the first channel and short the second channel to verify the PDaq is working. Is this a desktop or a laptop computer? I ask because if it is a laptop it could be floating the DAQ-3000 off ground. In this case connect the LVDT power supply ground to the AGND. 

 

2014-07-16_10-37-40.png

 

In addition, in working recently with an LVDT from Omega, the customer determined that it was NON LINEAR, and created a table of reference points to use with the Scaling module - that allows you to do a piecewise linear scaling.

Measurement Computing (MCC) has free technical support. Visit www.mccdaq.com and click on the "Support" tab for all support options, including DASYLab.
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